DE2557407A1 - Polyurethane-polyurea microcapsule prodn. - by reacting polyisocyanate (prepolymer) soln. with polyamines and removing the solvent - Google Patents

Abstract

Polyurethane-polyurea hollow capsules opt. contg. other substances are prepd. by (a) converting a di- or polyisocyanate and/or NCO prepolymer soln. in a low boiling solvent into small particles, (b) contacting the particles with di- and polyamines at raised temp. until a solid prod. is formed which is expanded by the evaporating solvent and (c) separating the capsules from the amine and solvent. The viscosities of the solns. are low and the process is easily carried out. The capsules are temp. stable and solvent resistant and may be used as fillers for e.g. concrete, plaster resins, etc., and as capsules for fertilisers, pesticides, insecticides, oils or solvents.

Description

Process for the production of polyurethane-polyurea-

Hotil pearls The object of the present invention is to provide a method to provide, which directly supplies hollow beads made of polyurethane polyureas, which pearls can also contain other substances included.

From the German Offenlegungsschrift 1 519 776 is a method become known for the production of microscopic hollow bodies, after which one the Solution of a polymer in a volatile organic solvent by a The same atomizer is atomized into fine spray droplets, the spray droplets into water vapor initiates and collects the microscopic hollow bodies obtained.

Both the method and the microscopic ones made after it However, hollow bodies have a number of disadvantages.

So the solutions used for spraying have a high Viscosity, which manifests itself in a strong tendency to string; the solutions are therefore difficult to spray.

This disadvantage could in principle be overcome by adding more solvent eliminate, but such a measure has other disadvantages. So much higher spray towers would have to be used due to the high solvent content be, and the solvent would in its double function according to the process as Viscosity reducers and as propellants with regard to the latter function are less exploited.

Naturally, only polymers can be used for the process of DOS 1,519,776 which are soluble in solvents, i.e. not crosslinked, are used. Because the microscopic Hollow bodies are formed by a simple physical inflation process, the finished hollow bodies are still uncrosslinked and in solvents soluble. As a result, the end products are very sensitive to it Solvents, because a mere softening of the polymer shell causes the Hollow bodies collapse, forming a liquid droplet. This sensitivity restricts the use of such microscopic hollow bodies in practice. Here would be cross-linked and consequently insoluble in solvents or opposite Solvent-insensitive hollow beads are much more suitable.

A process for the production of hollow beads is therefore the requirement to ensure that it can be carried out easily and with the lowest possible viscosity solutions is working. So that the hollow beads can be used as widely as possible, they should be cross-linked and therefore neither soluble in solvents nor in relation to solvents be sensitive.

Surprisingly, it has now been found that these requirements have been met can be if solutions of die or polyisocyanates and / or isocyanate groups containing prepolymers in a volatile solvent in an atmosphere be injected from a gaseous diamine or polyamine at elevated temperature.

The invention thus provides a method for producing Polyurethane-polyurea hollow beads, which may be

may contain other substances included, which is indicated by this is that you have a solution of a di- or polyisocyanate and / or an NCO prepolymer converted into small particles in a low-boiling solvent, the particles with a gaseous di- and / or polyamine at elevated temperature while in contact brings until it is converted into the solid state by polyisocyanate polyaddition and are inflated by the evaporating solvent and then by the gaseous The amine component and the solvent are separated off.

It is to be regarded as surprising that according to the invention Process at all hollow pearls arise. It would have been expected that the low-boiling solvent from the finely divided liquid droplets on entry into the reaction space due to the high temperatures prevailing there (up to 1500C) would volatilize immediately, so that no hollow bodies but homogeneous ones Powder particles would be formed.

The amines can be used alone or diluted with an inert gas will. The amine concentration (partial pressure) and thus the reaction rate can be specified can always be controlled within wide limits that initially by interfacial polyaddition a slight crosslinking takes place on the surface of the droplet and only then the Evaporation of the solvent sets in, which turns the individual particles into hollow beads finds.

For the purposes of the present invention, polyisocyanates are all known Di- and polyisocyanates; Examples include: aliphatic, cycloaliphatic, araliphatic, aromatic and heterocyclic polyisocyanates (cf. Ann. 562, Pages 75 to 136>, for example ethylene diisocyanate, 1,4-tetramethylene diisocyanate, 1,6-hexamethylene diisocyanate, 1,12-dodecane diisocyanate, cyclobutane-1,3-diisocyanate, Cyclohexane-1,3- and 1,4-diisocyanate and any mixtures of these isomers, 1 -Isocyanato-3, 3, 5-trimethyl-5-isocyanatomethyl-cyclohexane (DAS 1,202,785), 2,4- and 2, 6-hexahydrotoluylene diisocyanate and any mixtures of these isomers, Hexahydro-1,3- and / or 1,4-phenylene-diisocyanate, perhydro-2,4'- and / or -4,4'-diisocyanate, 1,3- and 1,4-phenylene diisocyanate, 2,4- and 2,6-tolylene diisocyanate, and any Mixtures of these isomers, diphenylmethane-2,4'- and / or -4,4'-diisocyanate, naphthylene-1 , 5-diisocyanate, triphenylmethane-4,4 ', 4-triisocyanate, polyphenyl-polymethylene-polyisocyanate (obtained by aniline-formaldehyde condensation and subsequent phosgenation according to British patents 874,430 and 848,671), perchlorinated aryl polyisocyanates (See Deutsche Auslegeschrift 1,157,601), polyisocyanates containing carbodiimide groups (see German patent specification 1,092,007), diisocyanates according to US patent specification 3,492,330, Polyisocyanates containing allophanate groups (see British patent specification 994,890, Belgian patent specification 761,626 and Dutch patent application 7,102,524), isocyanurate groups containing polyisocyanates (see German patents 1,022,789, 1,222,067 and 1,027,394; German Offenlegungsschriften 1,929,034 and 2,004,048), Polyisocyanates containing urethane groups (cf.

Belgian patent 752,261; U.S. Patent 3,394,164), acylated Polyisocyanates containing urea groups (cf.

German Patent 1,230,778) polyisocyanates containing biuret groups (See German patent specification 1,101,394, British patent specification 889,050; French 7,017,514), polyisocyanates produced by telomerization reactions (See Belgian patent specification 723,640), polyisocyanates containing ester groups (See British Patents 956,474 and 1,072,956; U.S. Patents 3,567,763; German Patent 1,231,688), as well as reaction products of the above-mentioned isocyanates with acetals (see German patent specification 1,072,385).

NCO prepolymers are reaction products of a stoichiometric excess of the above-mentioned polyisocyanates with at least two, preferably terminal OH groups containing compounds of medium molecular weight (approx. 400 to approx.

10,000). These products contain free - preferably terminal - NCO groups and react like polyisocyanates.

OH compounds which are particularly suitable for the production of the NCO prepolymers (Polyols) have a molecular weight of 400 to 10,000, preferably 1,000 to 5,000 and 2 to 8 hydroxyl groups per molecule. Polyesters are particularly suitable, Polyethers, polythioethers, polyacetals, polycarbonates and polyester amides. Examples for suitable polyesters are reaction products of polyvalent, preferably divalent and optionally additionally trihydric alcohols with polyhydric, preferably dibasic carboxylic acids. To produce the polyester can instead of the free Polycarboxylic acids also the corresponding polycarboxylic anhydrides or corresponding Polycarboxylic acid esters of lower alcohols or mixtures thereof can be used. The polycarboxylic acids can be aliphatic, cycloaliphatic, aromatic and / or heterocyclic in nature and optionally, for example by halogen atoms substituted and / or unsaturated. Examples include: succinic acid, Adipic acid, suberic acid, azelaic acid, sebacic acid, phthalic acid, isophthalic acid, Trimellitic acid, phthalic anhydride, tetrahydrophthalic anhydride, hexahydrophthalic anhydride, Tetrachlorophthalic anhydride, endomethylenetetrahydrophthalic anhydride, glutaric anhydride, Maleic acid, maleic anhydride, fumaric acid, dimeric and trimeric fatty acids, dimethyl terephthalate and terephthalic acid bisglycol ester. Polyhydric alcohols include, for example, ethylene glycol, propylene glycol (1,2) and - (1,3, butylene glycol (1,4) and - (2,3), hexanediol (1,6), Octanediol (1,8, neopentyl glycol, cyclohexanedimethanol (1,4-bis-hydroxymethyl-cyclohexane), 2-methyl-1,3-propanediol, glycerine, trimethylolpropane, hexanetriol- (1,2,6), butanetriol- (1,2,4), Trimethylolethane, pentaerythritol, quinite, mannitol and sorbitol, methyl glycoside, polyethylene glycols, Dipropylene glycol, polypropylene glycols, dibutylene glycol and polybutylene glycols are possible. The polyesters can have a proportion of terminal carboxyl groups. Also polyester from lactones z. e.g. g-caprolactone or hydroxycarboxylic acids, e.g. t »hydroxycaproic acid, can be used.

Suitable polyethers with 2 to 8, preferably 2 to 3, hydroxyl groups are for example by polymerizing epoxides such as ethylene oxide, propylene oxide, Butylene oxide, tetrahydrofuran, styrene oxide or epichlorohydrin with itself, e.g. in the presence of BF3, or through the addition of these epoxides, optionally in a mixture or one after the other, on starting components with reactive hydrogen atoms such as Water alcohols or amines, e.g. ethylene glycol, propylene glycol- (1,3) or - (1,2), Trimethylolpropane, 4,4'-dihydroxydiphenylpropane, aniline, ammonia, ethanolamine or ethylenediamine produced. Also sucrose polyethers such as those found in German Auslegeschriften 1,176,358 and 1,064,938 are described, come according to the invention in question. Often those polyethers are preferred which are predominantly (up to 90 wt. -%, based on all existing OH groups in the Polyether) primary Identify OH groups. Also modified by vinyl polymers polyethers, such as her e.g. by polymerizing styrene and acrylonitrile in the presence of polyethers arise (US patents 3,383,351; 3,304,273; 3,523,093; 3,110,695; German Patent specification 1,152,536) are suitable, as are polybutadienes containing OH groups.

Among the polythioethers are in particular the condensation products of thiodiglycol with itself and / or with other glycols, dicarboxylic acids, Formaldehyde, aminocarboxylic acids or amino alcohols are listed. Depending on the co-components If the products are polythio mixed ethers, polythioether esters or Polythioether ester amides.

As polyacetals come e.g. those from glycols, such as diethylene glycol, Triethylene glycol, 4,4'-dioxethoxydiphenyldimethylmethane or hexanediol and formaldehyde possible connections in question. Also by polymerizing cyclic acetals suitable polyacetals can be produced according to the invention.

Polycarbonates containing hydroxyl groups are those of the known type into consideration, e.g. by reacting diols such as propanediol- (1,3), Butanediol (1,4), and / or hexanediol (1,6), diethylene glycol, triethylene glycol, tetraethylene glycol with diaryl carbonates, e.g. diphenyl carbonate, or phosgene.

The polyester amides and polyamides include, for example, those made of polyvalent saturated and unsaturated carboxylic acids or their anhydrides and polyvalent ones saturated and unsaturated amino alcohols, diamines, polyamines and their mixtures recovered, predominantly linear condensates.

Also polyhydroxyl compounds already containing urethane or urea groups as well as modified natural ones, if necessary Polyols, such as castor oil, Carbohydrates, and starches, are usable.

Also adducts of alkylene oxides with phenol-formaldehyde resins or urea-formaldehyde resins can be used according to the invention.

Representatives of these compounds to be used according to the invention are for example, in High Polymers, Vol. XVI, "Polyurethanes, Chemistry and Technology" by Saunders-Frisch, Interscience Publishers, New York, London, Volume I, 1962, pages 32-42 and pages 44-54 and Volume II, 1964, pages 5-6 and 198 and 199, as well in the plastic manual, Volume VII, Vieweg-Höchtlen, Carl-Hanser-Verlag Munich, 1966, e.g. described on pages 45 to 71.

The production of NCO prepolymers from polyols and isocyanates is known (see R. Vieweg, A. Höchtlen, Kunststoff-Handbuch, Volume VII, Polyurethanes Carl-Hanser-Verlag, Munich 1966, pages 84 - 85).

Di- or polyamines in the context of the invention are preferably aliphatic Diamines, in particular alkylenediamines with 2-8 carbon atoms in the alkylene radical, such as ethylenediamine or propylenediamine or polyalkylenepolyamides such as dialkylenetriamines or trialkylenetetramines, the alkylene groups preferably containing 2 to 8 carbon atoms. examples are Diethylenetriamine, triethylenetetramine and preferably ethylenediamine. The amine component generally has a boiling point below 1500C, preferably below 1000C.

In order to reduce the brittleness of the process products, is used as the isocyanate component advantageously mixtures of monomeric di- or polyisocyanates and NCO Prepolymers, which at least 10, preferably at least 30% by weight of prepolymer with an average MI: lecular weight from 1,000 to 50,000, preferably from 2,000 to 20,000.

Suitable solvents are those with the isocyanate-containing Compounds are miscible and their boiling points between 0 and 140 ° C, preferably between 20 and 900cm. Those with boiling points have proven to be particularly advantageous between 40 and 700C, like acetone, methylene chloride and carbon tetrachloride or their mixtures.

The concentration of the isocyanate component in the solvent is generally between 65 and 90, preferably between 75 and 85% by weight.

The desired process products are therefore only within one very narrow concentration range. Both when using more than Even with less solvent, no hollow beads are formed, because once the hollow beads are formed burst if there is too much solvent and insufficiently inflated if too little will.

Second, the reaction speed (solidification of the outer skin the liquid droplets) should be too low if the solvent content is too high. To the For example, acetone has a slightly retarding reaction.

The method according to the invention is described below with reference to a preferred one Execution previously explained in more detail.

A di- or polyisocyanate and / or an NCO prepolymer is applied a temperature above its melting point but below its decomposition point brought and mixed with the solvent to form a homogeneous solution.

This liquid is in Shape smallest particles into one preferred tubular reactor introduced with gaseous di- or polyamine or an inert gas-amine mixture is filled, The temperature in the reactor must be above the boiling point or (if an inert Carrier gas is additionally fed in) above the dew point of the amine, above the evaporation point of the solvent and above the melting point of the NCO prepolymer, but below it Decomposition point. The initially liquid particles of the NCO-containing compounds remain in contact with the gaseous amine until they are through polyaddition are solidified and are then removed from the reactor. You then have them immediately Properties of free-flowing hollow beads.

You get a particularly quick reaction if you do the di-or Polyisocyanate or NCO prepolymer with a temperature below the dew point of the amine-inert gas mixture introduces into the reactor. The amine then condenses on the atomized particles. The condensation stops when the surface of the atomized particles is up has warmed up to the dew point.

The condensation of the amine can also be achieved by the arrangement of Control zones of different temperatures in the reactor. For example, at the entry point the isocyanate or NCO prepolymer particles have a temperature a little above the dew point, a higher temperature in the reactor itself and another one close to the reactor outlet Temperature should be provided a little above the dew point. Then amine condenses first on the particle, the unreacted part evaporates again, the particles become then cooled down a bit, but cannot stick together.

Since the boiling point and dew point of the amine are pressure-dependent, the Condensation of the amine can also be influenced via the reactor pressure. Advantageous A slight negative pressure, about 720-750 Torr, has been found; but you can also Provide overpressure or even lower pressure.

A continuously operating device for carrying out the process shows Figure 1. It consists of a tubular reactor (4), at the top End of a spray nozzle (3) is arranged, which in turn via a pump (2) with the Storage vessel (1) and a gas supply line (17) is provided. The gas is passed through a rotary knife (14) and gas heater (15) to the nozzle. To observe the atomization process is a sight glass (16) is attached to the head of the reactor. In the lower part of the reactor a first lateral approach (21) is provided above the evaporator (11) and of the pump (12) is connected to a further storage vessel (13), furthermore a second lateral approach (20) arranged with a heater (7) in connection stands, into which a gas can be introduced via a line (14). A third lateral approach (18) is in the upper part of the reactor via a fan (9), cyclone (8), cooler (6) connected to a washer (5). The reactor is also at the bottom Part provided with a removal device (10).

To carry out the process, a mixture is stored in the storage vessel (1) from an NCO prepolymer and / or a di- or polyisocyanate and the solvent presented and brought to the desired temperature. The isocyanate component is promoted via the pump (2) in the spray device (3), in the same time over the line (17) is an inert gas, e.g.

Nitrogen, is blown in. It then forms in the reactor (4) Mist made of NCO prepolymer or di- or polyisocyanate, Simultaneously a di- andX- or polyamine in brought the evaporator (11), there converted into the gaseous form and also into the Reactor headed. The mist of isocyanate and / or counter to this amine vapor of the NCO prepolymer reacts with polyisocyanate polyaddition to form the polyurethane / polyurea, a small part of the hollow beads formed in this way is via the fan (9) and the Cyclone (8) removed from the reactor and the separated gas flow in the cooler (6) and washer (5) worked up. Most of the hollow beads are at the bottom of the reactor taken. Inert gas, e.g. preheated nitrogen, to be brought into the reactor. Through this hot nitrogen the reactor is brought to reaction temperature before the start of the reaction and after Termination of isocyanate resp.

NCO prepolymer and amine feed blown empty.

The polyaddition, e.g. to the polyurethane-polyurea and the puffing to the hollow bead thus takes place in the flight phase of the atomized isocyanate or NCO prepolymer. The working temperature of the reactor depends on the starting materials used. It must preferably be above the boiling point of the amine used or the dew point with amine gas mixture.

It is particularly advantageous to work at reaction temperatures of 50-150 ° C .; the NCO prepolymer has a preferred temperature on entry into the reactor 20-120 ° C, the gaseous amine component has an inlet temperature of 120-140 ° C.

The amine is generally used in excess, the required Residence time (flight time) of the isocyanate droplets can range from a fraction of a second to a few Minutes, the necessary residence time is determined by the reaction temperature, the size of the particles and the relative amount of the amine. It can be shortened when amine is allowed to condense on the particles.

The residence time also depends on the type of isocyanate or NCO prepolymers and on the type of product desired.

It must be determined experimentally in each individual case by means of a preliminary test will. In general, the following applies: the smaller the isocyanate or NCO prepolymer particles more reactive the isocyanate resp.

NCO prepolymers and the amine, the greater the relative amount of amine and the higher the temperature, the shorter the residence time required. The temperature the isocyanate component should generally be lower than that of the amine.

Preferably, the temperature of the isocyanate component is reduced to one Set value that is 0 to 500C, particularly preferably 15 to 25 OC, below the boiling point or dew point of the amine component. It must also be noted that the Temperature of the isocyanate component sufficient (2 to 50 ° C, preferably 20 to 30 ° C) is below the boiling point of the solvent. Only in this case is ensures that the solvent does not volatilize prematurely in the reactor but is essentially only evaporated by the heat of reaction released, after being on the surface of the liquid droplets a reasonably stable Polyurethane urea shell formed <which then by the evaporating solvent into a hollow bead is raised.

Hollow pearls with liquid content always arise when the dwell time is set too short in relation to the particle diameter in the reactor. The reaction inside the particle is inhibited by the diffusion resistance of the already formed Polyurethane urea shell versus the amine.

You want instead of hollow beads made of fully reacted polyurea Manufacture those that only have an outer skin made of polyurea, but on the inside consist of polyurethane, the isocyanate component is mixed before spraying a less than equivalent amount of a slow reacting chain extender (e.g. one of the usual polyols such as ethylene glycol, butanediol, etc.) and leaves the sprayed liquid particles only so long in the amine atmosphere until in the Outer shell, the excess isocyanate has reacted with the amine. After that you can the formation of polyurethane continues in the interior of the hollow bead formed in this way.

It is also possible to add any desired isocyanate or NCO prepolymers to add other substances that do not take part in the polyisocyanate polyaddition. These substances are then encapsulated in the polyurethane-polyurea hollow beads or embedded in a matrix made of polyurethane or polyurea / polyurethane. This material is expediently dissolved or dispersed in the mixture of isocyanate respectively. NCO prepolymers and solvents before the start of the reaction and sprayed the so obtained mixture in the gaseous amine. Basically all are liquid and solid substances suitable for encapsulation, which are inert towards the reactants are.

Examples are: water-soluble salts such as phosphates, nitrates, Chlorides etc., e.g. all components of a mineral fertilizer, phosphoric acid ester, both water-soluble and insoluble, e.g. insecticides and pesticides, essential, vegetable and synthetic oils as well as high-boiling organic solvents.

In general, the amount of the substances to be encapsulated should be 1 to 95% by weight, based on isocyanate or NCO prepolymer. The mix must still be conveyable and atomizable.

The size of the polyurethane-urea hollow beads obtained is through the degree of division of the isocyanate or NCO prepolymer / solvent mixture is specified. It can be between about 10 and about 5,000 μm, preferably 10-200 μm.

The crosslinked produced by the process according to the invention and therefore hollow beads that are insensitive to solvents and are thermally stable can be used for a wide variety of purposes. Mainly they are fillers in a wide variety of substrates, such as bitumen, concrete, plaster, thermoplastic and thermoset Plastics, in which they contribute to volume expansion, by gluing the hollow beads it is also possible to use closed-cell foams to manufacture. The products are used in all areas in which there are no hollow beads containing substrates are used.

The invention is further illustrated by the examples given below explained. Unless otherwise noted, figures are given as parts by weight or Understand weight percentages.

Example 1 In a heatable reactor with a diameter of 600 mm and an overall height of 3 m according to FIG. 1 are continuously 10 kg / h of a mixture from: 1. 56 parts of a crude 4,4'-diphenylmethane diisocyanate with an NCO content of 30-32% and a content of 50% of higher-functional oligomers and homologues mix, 2. 24 parts of a prepolymer obtained by reacting 43.05 kg of a trifunctional, glycerine-based polyether made from 60% ethylene oxide and 40% propylene oxide (OH number 26; molecular weight 6500) with 6.95 kg of tolylene diisocyanate (80% 2,4- and 20% 2,6-isomer) for 6 hours at 950C (NCO content = 4.88 %; Viscosity at 400C = 3330 centipoise) and 3. 20 parts of acetone through a two-fluid nozzle sprayed at a temperature of 400C.

The isocyanate-solvent mixture is supplied with a rotary vane pump dosed from a storage tank and fed through the two-fluid nozzle with 10 Nm37h nitrogen atomized by 200C. In the lower part of the reactor 4.5 kg / h of ethylenediamine are added from a storage tank via a piston metering pump and evaporator with a temperature initiated by 1450C, in the reactor head there is a temperature of 700C, in the reactor body from 800C, there is a negative pressure of 5-10 Torr in the reactor. Takes place in the flight phase the chain extension in the atomized particles of the isocyanate component at the same time Inflation by the evaporating solvent.

At the foot of the reactor are continuously through a lock free-flowing, elastic hollow beads with a diameter of 20 - 200 / um and one Bulk density of 0.028 g / cm3 taken.

The gas mixture is fed to the cooler via a fan and cyclone, where the unused ethylene diamine gas and the solvent are condensed. Then the gas is released into the open via the scrubber.

Examples 2-11 The experiments were carried out according to the general procedure of Example 1. The ratio between monomeric isocyanate and NCO prepolymer, the solvent content and the amount of ethylenediamine were varied. Example ratio of acetone-ethylene-bulk remarks Isocyanate / content diamine weight Prepolymer quantity % kg / hg / cm³ 1 7: 3 20 4.5 0.028 free-flowing and very elastic 2 1: 3 20 4.5 0.01 well free flowing caves, through low Destructible by pressure 3 4: 1 20 4.5 0.024 free-flowing hollow pearls, with a slightly higher level Destructible by pressure 4 3: 2 20 4.5 0.024 free-flowing hollow pearls, with an even higher level Destructible by pressure. 5 1: 1 20 4.5 0.014 oval cave pearls 6 1: 1 15 4.5 0.017 hollow oval pearls 7 1: 1 10 4.5 0.028 almost felt-like fleece made of very oval hollow len 8 1: 1 25 4.5 0.027 free-flowing 9 1: 1 30 4.5 0.023 free-flowing 10 7: 3 20 4.0 0.032 free-flowing 11 7: 3 20 5.0 0.025 good free-flowing, mottled elasticity L eerseite

Claims (6)

Claims Process for the production of polyurethane-polyurea Hollow beads, which may contain other substances included, thereby characterized in that solutions of a di- or polyisocyanate and / or an NCO prepolymer be converted into small particles in a low-boiling solvent, the Particles with a gaseous di- and / or polyamine at elevated temperature for as long stay in contact until they become solid by polyisocyanate polyaddition transferred and inflated by the evaporating solvent and the hollow beads then separated from the gaseous amine component and the solvent. 2) Method according to claim 1, characterized in that the solution the isocyanate component has a temperature below the boiling point or The dew point of the amine component. 3) Method according to claim 1, characterized in that the Contact with the gaseous diamine or polyamine breaks off as soon as the particles form the Isocyanate component have formed a solid shell. 4) Method according to claim 1-3, characterized in that one of the Solution of the isocyanate component adds an inert solid or liquid substance, 5) Process according to claim 1 to 4, characterized in that the solution of the Polyisocyanate and / or the NCO Slowly prepolymers before spraying reacting chain extenders add and the atomized particles only as long as brings the gaseous diamine or polyamine into contact that a solid shell is formed, but the polyisocyanate component has not yet reacted completely. 6) Device for performing the method according to claim 1.